In the field of environment testing, a number of standardized methodologies for the determination of volumetric flow from an emissions source are codified in 40 CFR 60, Appendix A. One methodology, referred to as Method 2G, utilizes a 2-D probe, defined as a directional probe that measures velocity pressure and the yaw angle of gas flow, or a 3-D probe, which also measures a pitch angle of the flow, within the emissions source to determine the volume of emissions through the source. Small errors in the determination of the yaw angle in either direction can generally cause an overestimation of the volumetric flow through the emissions source. Since the determined volumetric flow is used over a reasonably long period of time (e.g., several months to a year) to estimate the emitted mass of a given substance at the emissions source, small errors in the flow determination can result in significant overestimation of the emitted mass over that period. Owners of power plants and other emissions sources must purchase credits for the amount of each pollutant they emit, making an overestimation of emitted pollutants a significant, unnecessary expense.